Jenn randomly chooses a number J from 1,2,3, \ldots, 19,20. Bela then randomly chooses a number B from 1,2,3, \ldots, 19,20 distinct from J. The value of B-J is at least 2 with a probability that can be expressed in the form \frac{m}{n} where m and n are relatively prime positive integers. Find m+n.